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What is TPMS and Why is it Important?

Are you seeing that little, yet alarming, yellow light with the exclamation mark popping up on your dash? If you’re a new driver, this light may come as a shock. You may be wondering what triggered it and how urgent this particular situation could be.
As the name suggests, your tire pressure monitoring system (TPMS) light coming on typically means your tire pressure is low. However, sometimes it turns on due to a drastic drop or rise in temperature. So, when do you know to act urgently? If your light turns on merely because of a temperature change, your light will turn off within one day. If your light stays on, it could be due to a tire puncture causing a slow leak of air.

​​​​​​​Your TPMS helps you to avoid potentially unsafe situations by monitoring the air pressure in your tires and alerting you when one of them drops by 25 percent or more below its recommended pressure. Your dashboard will display either the official TPMS symbol or a graphic indicating which tire is in need of air. It can be tough to tell if the air in a tire is too low or too high just by looking at it. When you see this light, bring your vehicle into Pep Boys for a tire pressure check.

Troubleshooting When My TPMS Light:

Illuminates While Driving

If your TPMS light comes on and continues to stay on, at least one of your tires has a low pressure level. If your car does not have the feature that shows which tire is low, make sure you check the pressure of all of your tires. You can do this by visiting a local garage or with a gauge.

Goes on & off

Keep in mind that fluctuating temperatures may be causing your TPMS light to turn on and off. In fact, for every 10 degrees, your tires will either drop or increase by 1 psi. Once you begin driving around, your light might turn off due to the rising temperature and/or heat generated from your vehicle. However, even if you’re light goes off, you should still use a gauge to check your tire pressure. If your TPMS light continues to go on and off, there’s a chance that one or more of your tires is below the optimal air pressure threshold.

Is Acting Up

If the light flashes for over a minute every time you start your car and then remains illuminated, this means your TPMS isn’t functioning properly and you should take it to an automotive service center for an inspection. Until repaired, continue to check the air pressure of all of your tires with a gauge, and add air to the tires that need it.

Should I be Concerned When the TPMS Light Comes on?

That depends on how long it has been on. Your TPMS light will typically come on when the weather has gone from somewhat warm to stark cold. Drastic changes in temperature could deplete or inflate air pressure in your tires causing your TPMS sensor to trigger. Waiting a day or two after the light comes on to get your tires checked won’t be the end of the world. However, if you ignore it for too long, you could find yourself in a bit of trouble. Below are the disadvantages to under-inflated tires:

  • Gas mileage will go down
  • Shortened tire life due to uneven tread wear
  • Decreased ability in steering handling
  • Tire blowout due to stress from under-inflation

What If My Car Doesn't Have a TPMS Light?

Not every car has a TPMS sensor to warn you about low air pressure in your tires. If this is the case, then develop a habit of checking your tires at least every 3–4 months. The most important times to check are during the fall and winter when temperatures are drastically changing. Checking your air pressure towards the ends of these seasons is best to make sure that your tires are ready for the beginning of winter and for the beginning of spring.

Maintain Proper Tire Inflation

Even if you have a tire pressure sensor, it’s important to check your air pressure regularly - as your vehicle’s age and other factors can impact the system’s readings. If you get the TPMS warning, simply check your driver’s side doorjamb or glove box of your vehicle for the recommended tire pressure, and fill the tire to spec. Your car will handle better, you’ll save gas and, ultimately, you’ll be safer on the road. Properly inflated tires are critical to stability, traction, steering, handling and braking. Guarantee yourself some peace of mind and make sure your tire pressure monitoring system is functioning properly with a check-up.

Tire Pressure Monitoring Sensors

Most vehicles use a direct system, in which a tire pressure sensor is in each tire. That sensor is linked to your vehicle’s onboard computer to directly measure air pressure.

A small number of vehicles use an indirect tire pressure monitoring system, which monitors the relative speed and rotation of the vehicle’s wheels and alerts you if one wheel is significantly out of sync with the others.

Underinflated tires can take a toll on your wallet and your safety by affecting your gas mileage and shortening tire life due to uneven wear. Even more importantly, underinflation can stress a tire to the point of failure, putting you in jeopardy of having a blowout on the road.

Tire Pressure

There are many things that can come into play and affect tire pressure, including temperature changes, tire punctures, or other damage. Tire pressure can drop about 1 psi (pounds per square inch) for every 10 degrees and tires lose about 1.5 psi per month as air escapes from the tire naturally.

On cold mornings, the TPMS light lamp may light up for a brief period and then turn off. This usually is caused by slightly low tire pressure that falls below the warning threshold overnight, but returns to an acceptable level as the tires heat up. In the summer, tires can overinflate, also triggering your TPMS light. If you notice this happening, bring your car into Pep Boys for a free tire pressure check.

TPMS is required by The National Highway Traffic Safety Administration on all vehicles produced after September 2007. Some earlier models may also come equipped with TPMS. Check your owner’s manual to be sure. According to the National Highway Traffic Safety Administration, TPMS is estimated to reduce the number of annual motor vehicle crash fatalities by about 120 and the annual number of injuries due to motor vehicle crashes by about 8,500, when all passenger vehicles are equipped with TPMS.

Many people think they should inflate their tires to the pressure that’s molded into the side of the tire. This is not the case. Vehicle manufacturers determine proper tire pressure based upon the vehicle’s weight distribution.

As a matter of safety, be sure to always use the manufacturer’s recommended tire pressure, which is listed in the owner’s manual and also on a sticker that’s attached to the driver’s side door jamb.

Indirect TPMS

Indirect TPMS works with your car’s antilock braking system’s (ABS) wheel speed sensors. If a tire has low air pressure, it rolls at a different wheel speed than the other tires. An indirect TPMS does not actually measure tire pressure. Instead, it measures how fast your tires are rotating and sends signals to the computer that will actuate the indicator light when something in the rotation seems incorrect.


  • Inexpensive in comparison to the direct TPMS
  • Requires less programming and maintenance over time than direct TPMS
  • Less installation maintenance than its direct counterpart


  • May become inaccurate if you purchase a bigger or smaller tire
  • May be unreliable when tires are unevenly worn
  • Needs a reset after properly inflating every tire
  • Must be reset after routine tire rotation

Direct TPMS

Direct TPMS uses a sensor mounted inside the wheel to measure air pressure in each tire. When air pressure drops 25% below the manufacturer’s recommended PSI level, the sensor transmits that information to your car’s computer system and triggers your dashboard indicator light.


  • Deliver actual tire pressure readings from inside the tire
  • Remains accurate, despite tire rotations or replacements
  • Simple resynchronization after tire rotation or tire replacements
  • Long lasting batteries (~10 years)
  • Typically included in a vehicle’s spare tire


  • Resynchronization can require costly tools
  • Battery is rarely serviceable—if the battery is drained then the whole sensor must be changed
  • These systems can make installation, service and replacement confusing for consumers and auto shops
  • Sensors are susceptible to damage during mounting and demounting

Remember, TPMS is not a cure-all or a replacement for proper air pressure maintenance—it’s important to check your air pressure regularly. Vehicle aging and other factors can impact the system readings. Your car will handle better, save you gas, and you’ll be safer on the road.

Nonetheless, if your TPMS light comes on, you should check your tire pressure. You can locate your recommended tire pressure in your owner’s manual or in the doorjamb of your driver’s side door. Or, if you’d like one of our ASE-certified technicians to take a look, schedule a free tire pressure check at your nearest Pep Boys.